1. Field of the Invention
The present invention relates to a heat exchanger to be used, for example, in refrigerator/air conditioners, and more particularly a finned heat transfer tube provided on an external surface thereof with fins for promoting heat conduction, a heat exchanger and a refrigerator/air conditioner.
2. Description of the Related Art
Japanese Patent Examined Publication No. 52-42255 (Literature 1) and Japanese Patent Unexamined Publication No. 63-197886 (Literature 2) are known as the conventional arts for what we call an independent fin tube heat exchanger in which a plurality of fins each having a through hole are inserted over a heat transfer tube. Literature 1 discloses a method for manufacturing a heat exchanger by forming through holes in a belt-like strip material, forming collars around the through holes, forming fins which have the same shape by cutting the strip material between the through holes, constituting blocks by overlapping the fins in a plurality, passing a heat transfer tube through the through holes after arranging the blocks in a row and forming this heat transfer tube so as to meander by sequentially bending it between the blocks. Further, Literature 2 discloses a heat exchanger provided with a large number of small fins wherein predetermined inter-row pitches are formed by interposing, between inter-row pitches, two heat exchangers which are provided with small fins and heat transfer tubes running through the small fins and are formed by bending the heat transfer tubes so as to meander at a pitch at least twice as large as a fin width in an air low direction of the small fins.
Further, techniques disclosed by Japanese Utility Model Unexamined Publication No. 61-26977 (Literature 3), Japanese Utility Model Unexamined Publication No. 3-31230 (Literature 4) and Japanese Utility Model Unexamined Publication No. 63-74983 (Literature 5) are known as arts (technique) for enhancing water dripping properties of divided heat exchangers. Literature 3 discloses a heat exchanger which has a slanted joined surface in a finned heat exchanger divided into an upper stage and a lower stage is slanted, Literature 4 discloses a heat exchanger in which lower ends of independently formed separate upper and lower fins are slanted, and Literature 5 discloses a heat exchanger in which lower ends of fins are disposed zigzag along rows of heat transfer tubes which are arranged in alternate rows.
The heat exchangers disclosed by Literatures 1 and 2 mentioned above which use the fins separated from each other pose problems that their strengths are lowered when they are piled up as heat exchangers in a direction of gravity and that their dripping properties are low when they are used as evaporators.
On the other hand, the heat exchangers disclosed by Literatures 3 through 5 mentioned above are configured for obtaining enhanced water dripping properties, but raise a problem that water dripping properties cannot be sufficiently enhanced simply by slanting the lower ends of the fins or configuration the lower ends in the zigzag shapes.